Amoebae of the genus Naegleria have been shown to harbor an infectious agent (Naegleria amoeba infectious agent or NAIM) recognized by its ability to produce cytopathic changes in tissue culture assay systems and, possibly, mice. This agent, in conjunction with thermal tolerance of the amoeba, may be a factor in determining the pathogenicity of Naegleria fowleri for humans, as the causal agent of primary amoebic meningoencephalitis. Research efforts will be directed toward: 1) Characterization of NAIM using crude amoeba lysates, medium from cytopathic tissue culture systems, and brain homogenates from inoculated animals; passing these preparations through Sephadex columns and/or one- and two-dimensional gel electrophoresis systems; 2) Assay of NAIM on a variety of tissue culture cell lines, both vertebrate and invertebrate, to determine responsiveness of cells to NAIM and to study, using the electron microscope, the nature of the cytopathic effect, if any; 3) Inoculation of experimental animals with NAIM, attempting to produce amoebic meningoencephalitis-like symptoms. Brain tissue homogenates will then be tested on tissue culture assay systems for cytopathology, and used for column fractionation and/or gel electrophoresis; and 4) Use of various chemicals and/or drugs to study the progress of the cytopathic effect in tissue culture cell lines, in the hope of visualizing the infectious agent at the electron microscope- level.